A J-shaped relationship between body mass index and the risk of elevated liver stiffness: a cross-sectional study

Liver stiffness (LS) is regarded as an indicator of the stages of liver fibrosis and liver cirrhosis. Numerous studies have investigated the relationship between body mass index (BMI) and LS; however, the conclusions remain controversial. In the current study, we utilized transient elastography (TE) technique, which could measure LS in a non-painful and noninvasive way, to explore the relationship between BMI and the risk of elevated LS in common community residents.

5791 participants were included in the present study. To calculate BMI value, height and weight of the participants were carefully measured. Liver stiffness measurement (LSM) > 9.1 kPa was considered as a cutoff suggesting elevated LS. The relationship of BMI and risk of elevated LS was derived using generalized linear regression models, and the threshold effect was then analyzed by smooth curve fitting and segmented regression model.

Elevated LS was detected in 230 participants (3.97%) using the TE technique. After potential confounders were adjusted according to the individual's demographic variables, underlying comorbidities and blood biochemical test results, we observed a J-shaped relationship between BMI and the risk of elevated LS, with the inflection point at 23.05 kg/m². The effect size (and confidence interval) was 0.84 (0.71, 0.98) on the left side of the inflection point, and 1.32 (1.24, 1.41) on the right side of it.

Our study found a novel J-shaped relationship between BMI and the risk of elevated LS assessed by TE technique. Abnormal BMI, either higher or lower, was associated with an increased risk of elevated LS.